A prefilled syringe is normally made by first sterilizing and drying the open syringe body. Then it is filled with the required medicament and capped. At the end of the process the filled and capped syringe is packaged.
The syringes are normally labeled so that the user can determine that he or she has the right product. Clearly it is critical that the contents match the label, as otherwise serious accidents could occur. In fact the label typically not only identifies the medicament and dose size, but also the production date and the expiration date. Other information such as price, producer's code, and batch number can also be printed on the syringe or on a label attached to it.
The labeling serves primarily for the user to determine that the right medicament is being or has been administered. It is often difficult or impossible to read and serves little function during the actual production of the syringe.